garmin_current_datetime

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the behavioral burden. It clearly states that the tool returns both local and UTC datetime variables and gives a concrete format example (YYYY-MM-DD). It does not explicitly mention side effects, but 'Return' and the utility framing make it evident this is a read-only operation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no filler. The core behavior is stated first, followed by practical usage guidance. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter tool with an output schema and a focused purpose, this description is complete. It explains what the tool returns, the relevant time scopes (local and UTC), and how the result should be used.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There are zero parameters, so the schema carries no burden and the baseline is 4. The description adds useful supporting meaning by showing how the returned values are meant to be consumed, including the YYYY-MM-DD format pattern for day/sleep/weight tools.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('Return') with a clear resource ('current date and time variables (local and UTC)'). It also positions the tool as a date/time utility for other Garmin tools, making it easy to distinguish from data-heavy siblings like garmin_daily_summary or garmin_activities.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly states when to use the tool: 'Use for building date ranges or passing today's date to other Garmin tools'. It does not discuss exclusions or alternatives, but for a simple utility tool with no obvious sibling competitor, this is clear context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.